1. INTRODUCTION TO WIRELESS PC COMMUNICATION
In many situations a communication link between two devices becomes essential. This communication can be wired or wireless. If two devices are close to each other a wired link is preferred. However in many situations two devices are reasonably far apart. In that case a wireless link is preferred. One of the popular wireless communication technologies is RF communication that is being used in our project.
The HT12E and HT12D chips have been used to maintain a wireless link between the two computers. The PC on the transmitter side first transmits the data serially to the microcontroller with the help of voltage converter (MAX232) at an adjusted baud rate. This data is then transmitted to the microcontroller on the receiver side with the help of the wireless link maintained by the RF module. This received data is then sent to the receiver PC serially.
The RS-232 cable (DB-9 connector in this case) is used to coordinate the serial communication between the computer and the microcontroller. The RS232 standard is not TTL compatible, but the 8051 has two pins, that are used specifically for transferring (P3.1) and receiving data (P3.0) serially which are TTL compatible; therefore it requires a line driver such as the MAX232 chip to convert RS232 voltage levels to TTL levels, and vice versa.
Once the microcontroller has serially received data from PC, the RF module comes into operation. For RF communication the HT12E IC installed at the transmitter side sends 12 bit data (8-bit address and 4-bit data) to the HT12D IC at the receiver side. If the 8-bit address at both the IC’s matches then 4-bit data is transmitted successfully to the microcontroller at the receiver side. Next the data is sent to the PC from the microcontroller via serial communication in a similar manner as in the case of the transmitter.
2. LITERATURE SURVEY
‘The 8051 Microcontroller and Embedded Systems’ by Muhammad
References:  Li-Jun Lai (2009),"radio remote control of appliances", paper, Institute of Electrical Engineering, National Yunlin University of Science and Technology, Touliu, Yunlin 640, Taiwan.